Micropropagation and Androgenesis in coconut: an assessment of Sri Lankan implication

Abstract

The coconut palm is an important cash crop mostly in the sub-tropical countries which provides almost all the necessities of life to the mankind. Genetic improvement for increased productivity is a prioritized research area of coconut palm. In vitro cloning of elite palms via somatic embryogenesis seems to be a promising method due to its potential for massive propagation. Based on the Sri Lankan experience, this paper summarizes the notable achievements towards developing a reliable protocol for clonal propagation of coconut and also dihaploid plant production. The newel explants described by Coconut Research Institute Sri Lanka (CRISL), unfertilized ovaries dissected from immature inflorescences collected from -4 stage (inflorescence to be opened in 4 months time), is a somatic tissue which causes minimal damage to the mother palm while collecting. Limited number of female flowers in an inflorescence which limits large scale culturing could overcome by callus multiplication phase to produce higher number of plants. Somatic embryogenesis and germination of somatic embryos was achieved by reduction of auxin concentration in the culture medium followed by an addition of cytokinin. AINTEGUMENTA-LIKE (ANT-like) gene isolated from coconut genome which shows higher conserved domain sequence similarities with BABYBOOM gene will assist development of suitable molecular markers to assess the morphogenic potential of in vitro cultured coconut tissues and callus. Successful plant regeneration from cultured anthers was reported by culturing anthers at three weeks before splitting (3-WBS) inflorescence stage which contains late uninucleate microspores. Heat pretreatment of anthers for six days at 38°C induced androgenesis in coconut upon culturing in 2, 4-D and 1-naphthyl acetic acid (NAA) added medium. Current clonal propagation protocol is efficient when responsive genotype is in use.Further improvement to current protocol will enable commercially viable protocol for coconut micropropagation.